The present invention relates to a new and improved method of, and apparatus for, opening folded, bound or stitched multi-sheet products, especially printed products.
Generally speaking, the method and apparatus of the present development is of the type wherein, by means of a preseparation element, a portion of the sheets are displaced in relation to the remaining sheets of the product while forming an opening.
In German Patent Publication No. 2,447,336, published Apr. 17, 1975 and the corresponding U.S. Pat. No. 3,951,399, granted Apr. 20, 1976 there is disclosed an article opening device wherein a pressure element exerts a pressure or compressive force upon the product. This compressive force extends transversely with respect to a flat side of the product. Consequently, there is brought about a bowing-out of part of the product. In the thus formed gap there is introduced a separation element which completely opens the product. Since the mode of operation of this apparatus is predicated upon the presence of a pre-bias, caused by a product fold, in the product it is only possible to open with this technique certain types of products. Additionally, during the pre-separation the gap always tends to form between the sheets located at opposite sides of the fold, so that opening of the product at a different location is not readily possible.
A method and apparatus of the previously mentioned type is known from Swiss Pat. No. 521,911, granted Apr. 30, 1972. In this case a roll or roller co-travels along with the printed product, this roll pressing against a flat side of such product and its direction of movement however being oriented at an inclination with respect to the direction of movement of the product. Due to its movement component extending at right angles with respect to the direction of movement of the printed product this roll causes displacement of one part of the printed product in relation to its other part in the direction of the product fold. Such results in bowing-out of the displaced part of the product. For completely opening the product a separation element is introduced into the formed opening. However, if there are not employed special measures the printed product, as a rule, will be opened at its centre. If opening of the product is desired at another location, then it is necessary to reduce the friction between the product sheets located at the separation location, for instance, by applying a dry lubricant. Moreover, this known apparatus is afflicted with the drawback that due to the frictional contact or connection between the roll and the printed product there exists the danger that the product can be damaged.
Other prior art constructions of product handling equipment have been disclosed in U.S. Pat. Nos. 3,580,562, 3,692,301 and 3,722,877.